1. Field of the Invention
The present invention relates to a method and an apparatus for generating sentences from given conceptual structures as elements of the sentences.
2. Description of the Background Art
In a conventional apparatus for generating sentences, a form of expression and order of words in a sentence to be generated are uniquely determined once the conceptual structures for the sentence matches with a certain prescribed pattern. For this reason, in generating a sentence, it has conventionally been impossible to select a form of expression which is suitable from a point of view of a balance of the sentence as a whole, out of a number of different forms of expressions having equivalent meanings.
As an example, consider a case of generating an English sentence from a concept ". . . ing . . . is good enough". In this case, two expressions "What is needed is to . . . " and ". . . ing . . . is sufficient" may be considered. Here, when a partial structure ". . . " is lengthy, the latter choice would result in a rather awkward sentence in which the subject is disproportionately large, so that the choice of the former would be preferable. On the contrary, when the partial structure ". . . " is short, the choice of the latter may be appropriate. However, this type of a choice of the form of expression has been impossible in the conventional apparatus for generating sentences.
As another example, consider a case of choosing an arrangement of the order of words. Namely, in English it is generally preferable to place a lengthy or complicated phrase toward the end of the sentence. Thus, for example a sentence "He had called the man on whose judgement he now had to rely an idiot." is rather awkward albeit grammatically correct. Alternate arrangement "He had called an idiot the man on whose judgement he now had to rely." would be less awkward and may be more preferable. Again, this type of a choice of the order of words has been impossible in the conventional apparatus for generating sentences.
It can be seen from these examples that, in order to be able to select an appropriate choice for the form of expression or the order of words from a number of possible candidates in a process of sentence construction, it is necessary to be able to assess a size of a partial structure of the sentence. However, the conventional apparatus for generating sentences has been impossible to incorporate such function, so that unnatural or awkward sentences have often been generated by the conventional apparatus for generating sentences.